Abaqus/CAE provided many different kinds of spectrum options for contour plot of stress or strain. However, I found the two green colors in the middle of the default spectrum are very close to each other. As a result, it is very difficult to identify them in the contour plot. See the following picture of the two colors. 

Fortunately, there are two methods to make the contour plot look better. Of course, the first one would be changing the color in above mentioned window. The second method could be using the contour edges to show where the boundaries are between tow colors. 

You could also reduce the number of colors in the spectrum. That will help too.